Many medical complications are created by the total or even partial blockage of blood vessels of the body. The primary cause of these complications is, of course, the reduction or cessation of blood flow through the blocked vessels to the particular biological tissue which is fed by the vessel. Most commonly, a blockage, or stenosis, is formed in an artery as a result of plaque build-up in the artery. Further, it is not uncommon for several stenoses to occur sequentially in a single artery or to develop near one another in branches of a common central artery.
Several methods, or procedures, have been developed in the medical field for the purpose of removing or clearing stenoses from the vessels of patients. One well known procedure for accomplishing this is an angioplasty procedure such as is disclosed in U.S. Pat. No. Re. 33,561 which issued to Levy for an invention entitled "BALLOON AND MANUFACTURE THEREOF". Basically, in an angioplasty procedure, a deflated dilatation balloon is inserted into the vessel and is placed across the stenosis. Once the balloon is properly positioned, it is then inflated to dilate the artery and thereby clear the stenosis. Another, more recently developed procedure for clearing a stenosis, is an atherectomy procedure. The essential aspects of an atherectomy procedure are set forth in U.S. Pat. No. 4,895,166 which issued to Farr et al. for an invention entitled "ROTATABLE CUTTER FOR THE LUMEN OF A BLOOD VESSEL". As disclosed by Farr et al., in an atherectomy procedure the stenotic material is actually cut and removed from the artery.
Both the angioplasty procedure and the atherectomy procedure are typically accomplished indirectly wherein access to the stenosis is achieved through a peripheral artery. These procedures are in contrast to other known procedures used to clear arteries, such as a by-pass surgery, where direct access to the stenosis is achieved by entering the artery at or near the site of the stenosis. Despite their differences, the ultimate objective of all these procedures is to remove or alleviate the stenosis which is restricting blood flow through the artery.
Recent studies have indicated that for procedures wherein a stenosis is to be dilated, such as for an angioplasty procedure, the efficacy of the dilatation is enhanced by first incising the material which is creating the stenosis. With this knowledge, several devices for clearing blocked arteries have been proposed.
For example, U.S. Pat. No. 5,209,799 which issued to Vigil for an invention entitled "METHOD FOR MANUFACTURING A FOLDING BALLOON CATHETER" discloses a folding angioplasty balloon with attached atherotomes. Operationally, the atherotomes attached to the Vigil device are intended to produce a series of incisions in the stenosis as the angioplasty device is inflated, thereby reducing the force needed to dilate the stenosis.
In general, the use of attached atherotomes has been found to be highly efficacious. As a result, the basic idea of attaching atherotomes to an angioplasty balloon has led to the development of folding devices, like the Vigil device, which conceal the atherotomes until the balloon is inflated. It may be appreciated that concealment of the atherotomes, as accomplished by Vigil, fathers an important goal by preventing unwanted contact between the atherotomes and the patient's vascular system as the balloon is maneuvered into position across the stenosis.
One way in which the functionality of traditional angioplasty balloons may be improved, that may not be entirely addressed through the use of attached atherotomes, is the provision of an angioplasty balloon with may be controlled to produced incisions of varying depth. In greater detail, it may be appreciated that a particular stenosis may require either a large or a small amount of incision before an effective dilation may be performed. If an atherotome equipped balloon is used, however, the degree to which the stenosis will be incised will be determined by the size of the atherotomes attached to the balloon, effectively limiting the degree to which the incision depth may be varied.
In light of the above, it is an object of the present invention to provide a device and method for incising and dilating a stenosis in a vessel of a patient which provides the ability to control the depth of incisions created. Another object of the present invention is to provide a device and method for incising and dilating a stenosis in a vessel of a patient which protects the vessel from unwanted incisions as the device is positioned within the stenosis. Yet another object of the present invention is to provide a device and method for incising and dilating a stenosis in a vessel of a patient which is relatively simple to manufacture, is easy to use, and is comparatively cost effective.